[smurf]

I see them as guides for the complexity of development.

In the early 20th century the beginnings of mechanised food production over shadowed some states wooden ploughs... that is many states had not developed the iron plough. Other places did not use the wheel, in my own city it was believed that wheels would break the cobble stones, so they used sleds until wheels finally replaced them.

Semaphore towers in France and the UK when on to develop telegraphs. Rail net works competed against canals.

Warfare, medicines, energy etc all develop at different rates. Necessity is the mother of invention and therefore it is truly difficult to have a degree of abstraction to cater for the historical development of all humanity.